Aromatic polyamide-hydrazide films, consisting of p-phenylene terephthalamide, p-benzamide and/or terephthaloyl hydrazide recurring units may have conferred upon them high tenacity and thermal stability, according to their chemical structure. But they are extremely sensitive to humidity, due to the presence of hydrophilic groups, such as amides and hydrazides, in their molecular chains. For instance, they often show large water absorption such as more than 10%, large hygroscopic expansion, unstable tensile strength and modulus and poor electrical properties (dielectric loss, insulation resistance, etc.). They also show poor flatness (tending to curl) and insufficient thermal durability.
This invention provides improved aromatic polyamide-type films, characterized by excellent mechanical strength, thermal stability, hygroscopic dimensional stability and other excellent properties, and also relates to a method of manufacturing those films.